xdcr: dropped work_seq_to_snapshot_seq
xdcr: dropped work_seq_to_snapshot_seq

It's not being used anymore

Change-Id: I4a14aa192a997f012c3c06ed03a8cc90d63ed58a
Reviewed-on: http://review.couchbase.org/38445
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

membase/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,membase/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,membase/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,mschoch/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server